The invention is in the field of mine tunneling machines, such as machines for cutting variable cross-section mining tunnels.
The most common known method of forming large mining tunnels in rock is the drill-and-blast method using explosives which has many disadvantages, one of which is that it is very hazardous. Thus, there has been a long-felt need for a mobile mining machine capable of successfully cutting large mining tunnels in rock by mechanical means in order to replace the use of explosives.
Several prior art patents show mining machines which appear to be capable of rotating a cutterhead about a horizontal axis and swinging it across a work face about a vertical axis. Typical of these are Osterhus et al, U.S. Pat. No. 2,776,824; Bergmann, U.S. Pat. No. 3,307,879; Frenyo et al, U.S. Pat. No. 3,929,378; Sigott et al, U.S. Pat. No. 4,111,488; and Marten, U.S. Pat. No. 4,230,372. All of these prior art patents disclose machines employing toothed or ripper cutter elements rather than disc cutters.
Sugden et al, U.S. Pat. No. 4,548,442, teaches a mobile mining machine having a wheel-like cutterhead assembly and having a swing boom assembly located forward of a pitch boom assembly.
Sugden at al, U.S. Pat. No. 3,965,995 discloses a machine for boring a large diameter vertical hole having a rotatable cutterwheel mounted on the lower end of a tubular support. The cutterwheel is rotatable about the tubular support on an axis perpendicular to the axis of rotation of the cutterwheel. To bore the vertical hole, the rotating cutterwheel is advanced into the ground to make a first cut. The cutterwheel is then rotated on the tubular support to make a subsequent cut across the first cut. This process is repeated until the hole is bored.
Bechem, U.S. Pat. No. 4,045,088, discloses a mining machine which is characterized by oscillation of a so-called drilling head about a vertical pivot axis to arcuately drive a slot cavity, the head and the rotatable disc cutters carried thereby being oscillated through a horizontal angle of about 120 degrees. Plural disc cutters are canted in a diverging manner. No cutter movement is contemplated other than horizontal oscillation.
Stoltefuss et al, U.S. Pat. No. 3,873,157, discloses a tunneling or mining machine with the cutting device rotatably mounted on the forward end of a boom which is vertically and horizontally pivotable. The cutting arrangement involves two narrow wheels or rollers carrying pick-like cutters.
Spurgeon, U.S. Pat. No. 4,312,541, discloses a trench cutting machine comprising a main body assembly and a cutting wheel assembly. This coal mining machine moves plural rows of disc cutters horizontally about a substantially vertical axis to facilitate discharge to a conveyor. A cylinder is mounted transversely on the main body assembly and carries a pair of pistons which extend axially from each end of the cylinder. Gripper pads are provided on each piston to bear against the side walls of the trench. Each piston has an end face within the cylinder which, together with an inner side wall of the cylinder, comprises a pressure chamber adapted to force the pads against the trench. The main body and its cylinder are free to move laterally relative to the pistons when the cylinder is pressurized. Extensible arms are provided between the pistons and the main body assembly for forcing the main body assembly and its cutting wheel forwardly to progressively cut a trench. A steering assembly is provided to shift the main body assembly laterally relative to the pistons and about the central axis of the cutting wheel.
Also known is Wharton, U.S. Pat. No. 3,726,562, which discloses a coal mining machine having a cutterhead in the shape of a shallow cone rotatably mounted on the forward end of an elongate boom. The cutterhead, although not described in detail, appears to involve a series of picks as the cutting elements. It is not clear from the disclosure of the patent how the cutterhead is rotated and the patent disclosure does not contemplate any particular correlation between the rate of cutterhead rotation and the rate of cutterhead swing. The cutterhead is swingable both horizontally and vertically.
A need thus exists for a mobile mining machine having a cutterwheel assembly carried by a boom assembly in which the cutterwheel and the boom orbit, and optionally traverse, the mobile mining machine. The above configuration, as differentiated from prior art mining machines having a swing boom assembly and a pitch boom assembly, allows the cutting of a tunnel either having a low height to width ratio or a substantially equal height to width ratio, and optionally having no roof crown.
A need also exists for a mobile mining machine having a cutterwheel that is manipulatable so that its axis of rotation can take any substantially parallel direction with respect to the tunnel work face to more efficiently cut the lower corners of the tunnel.
A need also exists for a mobile mining machine having the above configuration in which the mobile mining machine has a gantry-type frame defining an inner portion substantially devoid of components. This gantry configuration allows workmen and mining support vehicles to work under the mobile mining machine (gathering muck, for example) during the mining operation.